In general, complex manmade structures, whether stationary such as buildings and bridges, or mobile such as moving vehicles operating on land, sea, air, or space, are normally made from many components attached together forming a complex structure. The design of attachment points, commonly known as joints, requires special skill for engineering design and analysis. A major part of this task is the selection of proper components, such as fasteners, for joining and fastening the structure together.
The main purpose and primary object in joint design is to facilitate the load transfer from one component of the structure to another component. The joined structure should be able to sustain the external and internal loads that may be experienced while performing its intended function. Loading may be in sustained static form or in a variable dynamic form. The functioning environment may be corrosive in nature affecting material properties and integrity of the fasteners and structural material. The operating environment may also undergo temperature changes affecting the load carrying characteristics of the joint and fastener.
Since humankind's original venture into building structures and moving vehicles, many types of fasteners have been conceived, developed, and used successfully. However, with a developing civilization the need for improved fasteners is always evident. One common feature in many conventional joint designs is to create holes, or apertures, in the joint components, typically referred to as work pieces, to insert and attach the components to each other by placing a suitable fastener in the matching holes. These fasteners, referred to by many different names and terms, are major contributors for constructing buildings, tools, vehicles, and other important structures that sustain the present form of civilization and human life in modern societies.
Typical fasteners used today are inherent with problems. As described in more detail below, although typical nuts and bolts are capable of carrying tensile and shear loads, when applying typical nuts and bolts in structures, a major disadvantage occurs as there is a lack of a hole filling feature. That is, a hole or space is remaining after insertion of the fastener. One common approach adopted to overcome this disadvantage is to provide a hole filling feature by installing a bolt or shear pin fastener in a small interference hole. However, this is not practical or recommended for composite structures, as interference fit installations cause damage such as cracks and delamination in the composite structure, thus compromising the integrity of the structural components.
Consequently, a fastener which alleviates the problems inherent in conventional fasteners as described previously is needed.